1. Field of the Invention
Constructors of well pumping apparatus, particularly in the oil fields, have developed equipment which can be acclimated to specific physiological conditions on situs. Of primary concern is the depth of the deposit to be recovered, and the industry has distinguished between "shallow" deposits ranging to a depth of 10,000 feet, and deposits below that range being, not surprisingly, designated as "deep".
Depth of the deposit is an obvious design parameter in that it is determinative of the length, and, thus, the weight of the column of fluid to be raised, which in turn directs the structural strength and power required.
As in any other commercial venture, the cost of doing business has a direct correlation to such factors as down time and costs of repair, and any improvements which results in a lessening of these negative factors inevitably results in a significant improvement in the "bottom line".
Reciprocating type pumps have received wide acceptance in cases where relatively viscous fluids are to be retrieved from subterranean deposits, as the most efficient for such purposes. This is so despite the problems inherent in such equipment when exposed to abrupt changes of direction under load. Such loading factors not only effect the useful life and maintenance schedule for such equipment, but the speed at which such equipment can be operated. Indeed, the operator must strike a meaningful balance between his desire to optimize profit by extracting the most product per unit of time, and the down time costs for maintenance.
In shallow well operations, the standard in the industry is commonly referred to as a "walking beam" pumping unit. Such units employ a powered gear reduction unit which is greatly over designed, simply to be able to withstand shock loading. The transmission drives rotating cranks, which in turn, causes a beam to oscillate about a fulcrum point. A forward end of the beam connects to a stringer to reciprocate the pump in the well.
In recognition of the inevitability of striking the compromise, as aforesaid, by virtue of the deficiencies in existing equipment, the present invention seeks to provide improvements in such equipment so as to permit the operator to overbalance that compromise in favor of profit, principally due to the fact of the 2.1 ratio or, in most cases, double the stroke of most walking beam units.
2. Overview of the Prior Art
One of the prime limiting factors in the performance of existing shallow well equipment is its ability to withstand rapid and repeated changes in loading for extended periods of operation. Virtually all elements of the unit structure are placed under great stress as the pump reaches the bottom of its stroke and begins upwardly. The simplistic answer to this quandary is to simply build the apparatus stronger. There are, however, practical limits, dictated to some extent by size, and to a large extent by cost, to the massiveness of the equipment. Those practical limits have been reached in the familiar walking beam pumping unit.
There have been several efforts to render the "walking beam" unit obsolete, as evidenced by Mayer U.S. Pat. No. 4,761,120. Mayer teaches the concept of substituting a hydraulic ram, which reciprocates on a slide instead of the gear reduction transmission currently in wide use. The ram drives a flexible chain, and uses complex set of hydraulic controls to sense and control movement of the pump stringer. The fallacy of this concept, and those akin to it, is that it is not adaptable, nor compatible with the vast amount of existing equipment, end it is a start from scratch approach. As will be apparent, the "beam" itself is used to translate the rotary motion of the power unit, to the reciprocating motion needed at the well head, and the prior art solution to this translation is to employ reciprocating power, such as the ram, in the first instance. Weaver U.S. Pat. No. 4,512,149 is a variation on the same theme.
Whatley U.S. Pat. No. 4,530,645 presents yet another hydraulic/chain drive combination, and to a limited extent, Bender U.S. Pat. No. 5,018,350 is of interest in that belting is used between the source of motive power and the sucker rod. Bender is, of course, a deep well application, and as in the other relevant art, relies on hydraulic power in a totally different environment, than the present invention.